Sloan Great Wall

Sloan Great Wall
Willem Schaap · CC BY-SA 3.0 · source
Name	Sloan Great Wall
Caption	Galaxy distribution map highlighting the structure
Discovery date	2003
Discovered by	Sloan Digital Sky Survey
Type	Galaxy filament / wall
Distance	~1.38 billion light-years
Redshift	~0.08
Length	~1.37 billion light-years

Sloan Great Wall is an immense galaxy filament identified within redshift survey data, notable for its scale among known cosmic structures. It was revealed through mapping efforts that combined galaxy redshifts and photometry, altering ideas about the distribution of matter in the nearby Universe. The feature lies in the region surveyed by a major sky program and has been compared with other large-scale structures in analyses of cosmological models.

Discovery and Observation

The structure was first recognized in data from the Sloan Digital Sky Survey during large-scale mapping that included redshift catalogs, imaging campaigns, and spectral analyses. Survey teams used instrumentation from the Apache Point Observatory and data pipelines developed by the Astrophysical Research Consortium to extract positions and velocities for member galaxies. Follow-up studies incorporated measurements from facilities such as the Two-degree Field Galaxy Redshift Survey, the Arecibo Observatory, and the Hubble Space Telescope for morphological classification and distance confirmation. Analysis papers appeared in journals produced by the American Astronomical Society and were presented at meetings organized by the International Astronomical Union, prompting comparisons with the CfA2 Great Wall, the Hercules–Corona Borealis Great Wall, and features in the 2MASS Redshift Survey. Teams from institutions including Princeton University, Harvard–Smithsonian Center for Astrophysics, University of Chicago, University of Portsmouth, and Max Planck Society contributed to mapping and interpretation.

Physical Properties and Size

The reported extent of the feature spans on the order of 1.2–1.4 billion light-years in comoving length, making it comparable to, and in some metrics larger than, structures like the CfA Great Wall and the Shapley Supercluster complex. Its redshift range centers near z ≈ 0.07–0.09, situating it at a comoving distance similar to that of the Coma Cluster and the Perseus–Pisces Supercluster. Mass estimates derive from galaxy counts, luminosity weighting, and correlation with dark matter inferred from surveys such as the Sloan Digital Sky Survey weak-lensing programs and the Planck microwave background lensing maps. The feature’s galaxy number density and luminosity function have been compared to field surveys like the Galaxy And Mass Assembly project and the DEEP2 Galaxy Redshift Survey to quantify overdensity and richness.

Structure and Composition

This filamentary wall comprises galaxy clusters, groups, and field galaxies arranged in sheets and filaments that connect known concentrations such as the Abell catalog clusters and X-ray–bright systems cataloged by the ROSAT mission. Member systems include rich clusters analogous to entries in the Abell catalogue and poorer groups identified in the Zwicky Catalog. The baryonic content spans stellar populations cataloged by surveys like the 2dF Galaxy Redshift Survey and gaseous components traced by observations from the Chandra X-ray Observatory and XMM-Newton. Dark matter halos inferred from dynamical studies and weak gravitational lensing, modeled using tools from the Millennium Simulation and the Illustris project, dominate the mass budget. Galaxy morphologies within the structure range from early-type ellipticals common in cluster cores to late-type spirals and irregulars typical of the Local Group environs, with star-formation trends investigated using data from the Galaxy Evolution Explorer and the Spitzer Space Telescope.

Formation and Cosmological Significance

Formation scenarios for such an extended feature follow hierarchical growth prescriptions found in the Lambda-CDM model and numerical simulations like the Millennium Simulation and Bolshoi simulation, where initial fluctuations amplified by gravitational instability produce sheets, filaments, and voids. The existence and scale of the wall inform statistical tests of cosmic isotropy and homogeneity invoked in the Cosmological Principle and constrain primordial power spectra measured by the Wilkinson Microwave Anisotropy Probe and Planck missions. Debates around the probability of forming structures of this size within Gaussian initial conditions involve theoretical work from researchers affiliated with institutions such as CERN, Institute for Advanced Study, and Kavli Institute for Cosmology. Observational implications extend to baryon acoustic oscillation measurements from surveys like BOSS and eBOSS and to studies of large-scale velocity fields probed by the 6dF Galaxy Survey and peculiar-velocity programs led by groups at Caltech and University of Hawaii.

Relationship to Large-scale Structure and Superclusters

The feature resides among a network of superclusters, voids, filaments, and walls that define the cosmic web mapped by the Sloan Digital Sky Survey and complementary projects including 2MASS, WISE, and the Dark Energy Survey. It connects or lies adjacent to superclusters cataloged in compilations derived from the Abell cluster catalogs, and its orientation and node connections have been studied relative to features like the Great Attractor region, the Bootes Void, and the Shapley Concentration. Comparative analyses use graph-theoretic and percolation methods developed in studies from the Institut d'Astrophysique de Paris and Max Planck Institute for Astrophysics to quantify filamentarity and connectivity among known superclusters such as Sloan Great Wall adjacent superclusters studies by teams at Yale University and University of California, Berkeley. The structure remains a reference point in discussions of the largest coherent matter distributions accessible with current redshift surveys and motivates future mapping by projects like the Dark Energy Spectroscopic Instrument, the Large Synoptic Survey Telescope, and the Euclid (spacecraft) mission.

Category:Cosmic structures